GM9.12

EDI
Interactions between tectonics, climate and surface processes from mountain belts to basins

The coupling between tectonics, climate and surface processes governs the dynamics of mountain belts and basins. First order constraints on this coupling are provided by geomorphic and sedimentary records, including longitudinal river profiles, fluvial terraces, downstream fining trends, growth strata, sediment provenance, sequence stratigraphy, and changing depositional environments. Moreover, the increasing integration of geochronological methods for quantifying erosion rates and source-to-sink sediment transfer with landscape evolution, stratigraphic, climatic, and tectonic models allows to advance our understanding of the interactions between surface processes, climate and tectonic deformation.

We invite contributions that use geomorphic and/or sedimentary records to understand tectonic deformation, climate histories, and surface processes, and welcome studies that address their interactions and couplings at a range of spatial and temporal scales. In particular, we encourage coupled catchment-basin studies that take advantage of numerical/physical modelling, geochemical tools for quantifying rates of surface processes (cosmogenic nuclides, low-temperature thermochronology, luminescence dating) and high resolution digital topographic and subsurface data. We also encourage field or subsurface structural and geomorphic studies of landscape evolution, sedimentary patterns and provenance in deformed settings, and invite contributions that address the role of surface processes in modulating rates of deformation and tectonic style, or of tectonics modulating the response of landscapes to climate change.

Co-organized by TS5
Convener: Duna Roda-BoludaECSECS | Co-conveners: Anneleen Geurts, Dirk Scherler, Alex Whittaker, Camille LittyECSECS, Julien Charreau
vPICO presentations
| Tue, 27 Apr, 11:00–15:00 (CEST)

Session assets

Session materials

vPICO presentations: Tue, 27 Apr

Chairpersons: Duna Roda-Boluda, Dirk Scherler, Anneleen Geurts
Tectonics, topography and drainage evolution
11:00–11:02
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EGU21-233
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ECS
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solicited
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Highlight
Armin Dielforder

The shear force along convergent plate boundary faults, called megathrusts, determines the height of mountain ranges that can be mechanically sustained. However, whether the true height of mountain ranges corresponds to this tectonically supported elevation is debated. In particular, climate-dependent erosional processes are often assumed to exert a first-order control on mountain height, although this assumption has remained difficult to validate. To address this issue, I first constrained the shear force along active megathrusts from their rheological properties and then determined the tectonically supported elevation using a force balance model. This analysis revealed that the height of mountain ranges around the globe matches the tectonically supported elevation, irrespective of climatic conditions and the rate of erosion. This finding indicates that the height of mountain ranges is effectively limited by the megathrust shear force and implies that global differences in mountain height are at first-order tectonically controlled. Thus, temporal variations in mountain height should reflect long-term changes in the force balance rather than changes in climate.

How to cite: Dielforder, A.: Megathrust shear force limits mountain height at convergent plate margins, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-233, https://doi.org/10.5194/egusphere-egu21-233, 2020.

11:02–11:04
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EGU21-8243
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ECS
Luuk van Agtmaal, Attila Balazs, Dave May, and Taras Gerya

The inherent links between tectonics, surface processes and climatic variations have long since been recognised as the main drivers for the evolution of orogens. Oceanic and continental subduction and collision processes lead to distinct topographic signals. Simultaneously, different climatic forcing factors and denudation rates substantially modify the style of deformation leading to different stress and thermal fields, strain localisation and even deep mantle evolution. An ideal area where the above-mentioned processes and their connections can be studied is the India-Eurasia collision zone.

Understanding the complex interplay between tectonics, erosion, sediment transportation and deposition requires the coupled application of thermo-mechanical and surface processes modelling techniques. To this aim, we used a 3D coupled numerical modelling approach. The influence of different plate convergence, erosion and sedimentation rates has been tested by the thermo-mechanical code I3ELVIS (Gerya and Yuen, 2007) coupled to the diffusion-advection based (FDSPM) surface processes model.

We show preliminary results to demonstrate  that the diffusion-advection erosion implementation has significant effects on local and regional mass redistribution and topographic evolution within narrow, curved, high orogens such as the Himalayas and their syntaxes, where erosion is a dominant forcing factor. We also discuss possible implications from different erosion/sedimentation implementations such as DAC (Ueda et al., 2015; Goren et al., 2014) in combination with the reference thermo-mechanical model to analyse changes in orogenic development as a consequence of different erosional processes in more detail.

References:

Gerya, T. V., & Yuen, D. A. (2007). Robust characteristics method for modelling multiphase visco-elasto-plastic thermo-mechanical problems. Physics of the Earth and Planetary Interiors, 163(1-4), 83-105.
Ueda, K., Willett, S. D., Gerya, T., & Ruh, J. (2015). Geomorphological–thermo-mechanical modeling: Application to orogenic wedge dynamics. Tectonophysics, 659, 12-30.
Goren, L., Willett, S. D., Herman, F., & Braun, J. (2014). Coupled numerical–analytical approach to landscape evolution modeling. Earth Surface Processes and Landforms, 39(4), 522-545.

How to cite: van Agtmaal, L., Balazs, A., May, D., and Gerya, T.: Surface processes control on orogenic evolution: inferences from 3D coupled numerical models and observations from the India-Eurasia collision zone, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8243, https://doi.org/10.5194/egusphere-egu21-8243, 2021.

11:04–11:06
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EGU21-16009
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ECS
Riccardo Reitano, Claudio Faccenna, Francesca Funiciello, Fabio Corbi, Pietro Sternai, Sean D. Willett, Riccardo Lanari, and Andrea Sembroni

In convergent systems, tectonics, erosion, and sedimentation control orogenic evolution. The nature of the interaction between these factors is still to be unraveled, because of their complex feedback that goes through different time and spatial scales. Here, we try to bind tectonics, erosion, and sedimentation by running laboratory-scale coupled analog models of landscape evolution, in which both tectonic forcing and surface processes are modeled, trying to unravel the nature of these multiple-interrelated processes. The analog apparatus consists of a rectangular box filled with a water-saturated granular material. The deformation is imposed by the movement of a rigid piston (backstop), while surface processes are triggered by simulated rainfall and runoff. We systematically vary the convergence velocity and the rainfall rate, testing how different boundary conditions affect the balance between tectonics and surface processes and the onset of steady-state configurations. We measure the competition between input fluxes (tectonics) and output fluxes (erosion) of material. The results show how analog models never achieve a steady-state configuration in which tectonic rates are perfectly balanced by erosion rates. Tectonics add more material to the accretionary wedge than is removed by erosion (about 2-5 times more). Still, erosional fluxes seem to reach an equilibrium with the applied tectonic flux. The foreland is always overfilled with sediments, and we argued how the storage of sediments in front of a wedge can strongly divert the orogenic system from the “classical” steady state configuration. This work analyzes which are the main differences between analog and theoretical models and if/how the results coming from analog models can be exportable when interpreting natural landscape morphologies and force balance.

How to cite: Reitano, R., Faccenna, C., Funiciello, F., Corbi, F., Sternai, P., Willett, S. D., Lanari, R., and Sembroni, A.: The (un)balance between tectonic and erosion in analog accretionary wedges, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16009, https://doi.org/10.5194/egusphere-egu21-16009, 2021.

11:06–11:08
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EGU21-15983
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ECS
Raphaël Melis, Véronique Gardien, Gweltaz Mahéo, Christophe Lécuyer, Philippe-Hervé Leloup, Patrick Jame, and Eric Bonjour

Paleoaltimetry is a powerful tool to study tectonic, climate and surface processes interactions. Indeed, stable isotope composition of meteoric water can be correlated with the elevation of reliefs. The δ18O and δD of orogenic rainfall decrease while the elevation increase. Current paleoaltimetric methods based on stable isotope, including the study of pedogenic carbonates and micas associated with fault or shear zones, represent an indirect way to obtain stable isotope « paleometeoric fluid » composition. These methods do not provide simultaneously the δ18O and δD values implying the use of isotope exchange equation, source of signficant errors (up to +/- 1000m).

We have developed a new method which allow to directly acces at both the δ18O and δD of « paleometeoric » fluids with a good precision and margin of error less than +/- 200m . This method has been developed on the stable isotope composition of fluid inclusion trapped in quartz veins. The developed experimental protocol allows to extract small quantity of fluid (~10mL) and directly analyse both the δ18O and δD with a OA-ICOS Spectroscopy. Tested on 18 Miocene alpine quartz veins from the Mont-Blanc and the Chenaillet massifs the stable isotope composition of the fluids fit very well with meteoric isotopic signature and highlight the robustness of stable isotope ratio through geological time.

More over, our results indicate that Miocene precipitation was way more positive (-4,8 to -9 ‰ for δ18O and -38,2 to 68,8‰ for δD) in the Mont-Blanc massif area than modern precipitation (-12,9 to -18 ‰ for δ18O and -101,1 to -144,25‰ for δD) which indicate that the massif was still at low elevation at this time. In contrast the « paleoprecipitation » of the Chenaillet massif fall in the same range than modern precipitation (-83 to -120,3 ‰ for δD and -11,8 to -16,9 ‰ for δ18O) which indicate this massif has already reached his present altitude (~ 2500m).

How to cite: Melis, R., Gardien, V., Mahéo, G., Lécuyer, C., Leloup, P.-H., Jame, P., and Bonjour, E.: Stable isotope composition of fluid inclusions in quartz minerals : New method for paleoaltimetry, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15983, https://doi.org/10.5194/egusphere-egu21-15983, 2021.

11:08–11:10
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EGU21-3135
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ECS
Jennifer Spalding, Jeremy Powell, David Schneider, and Karen Fallas

Resolving the thermal history of sedimentary basins through geological time is essential when evaluating the maturity of source rocks within petroleum systems. Traditional methods used to estimate maximum burial temperatures in prospective sedimentary basin such as and vitrinite reflectance (%Ro) are unable to constrain the timing and duration of thermal events. In comparison, low-temperature thermochronology methods, such as apatite fission track thermochronology (AFT), can resolve detailed thermal histories within a temperature range corresponding to oil and gas generation. In the Peel Plateau of the Northwest Territories, Canada, Phanerozoic sedimentary strata exhibit oil-stained outcrops, gas seeps, and bitumen occurrences. Presently, the timing of hydrocarbon maturation events are poorly constrained, as a regional unconformity at the base of Cretaceous foreland basin strata indicates that underlying Devonian source rocks may have undergone a burial and unroofing event prior to the Cretaceous. Published organic thermal maturity values from wells within the study area range from 1.59 and 2.46 %Ro for Devonian strata and 0.54 and 1.83 %Ro within Lower Cretaceous strata. Herein, we have resolved the thermal history of the Peel Plateau through multi-kinetic AFT thermochronology. Three samples from Upper Devonian, Lower Cretaceous and Upper Cretaceous strata have pooled AFT ages of 61.0 ± 5.1 Ma, 59.5 ± 5.2 and 101.6 ± 6.7 Ma, respectively, and corresponding U-Pb ages of 497.4 ± 17.5 Ma (MSWD: 7.4), 353.5 ± 13.5 Ma (MSWD: 3.1) and 261.2 ± 8.5 Ma (MSWD: 5.9). All AFT data fail the χ2 test, suggesting AFT ages do not comprise a single statistically significant population, whereas U-Pb ages reflect the pre-depositional history of the samples and are likely from various provenances. Apatite chemistry is known to control the temperature and rates at which fission tracks undergo thermal annealing. The rmro parameter uses grain specific chemistry to predict apatite’s kinetic behaviour and is used to identify kinetic populations within samples. Grain chemistry was measured via electron microprobe analysis to derive rmro values and each sample was separated into two kinetic populations that pass the χ2 test: a less retentive population with ages ranging from 49.3 ± 9.3 Ma to 36.4 ± 4.7 Ma, and a more retentive population with ages ranging from 157.7 ± 19 Ma to 103.3 ± 11.8 Ma, with rmr0 benchmarks ranging from 0.79 and 0.82. Thermal history models reveal Devonian strata reached maximum burial temperatures (~165°C-185°C) prior to late Paleozoic to Mesozoic unroofing, and reheated to lower temperatures (~75°C-110°C) in the Late Cretaceous to Paleogene. Both Cretaceous samples record maximum burial temperatures (75°C-95°C) also during the Late Cretaceous to Paleogene. These new data indicate that Devonian source rocks matured prior to deposition of Cretaceous strata and that subsequent burial and heating during the Cretaceous to Paleogene was limited to the low-temperature threshold of the oil window. Integrating multi-kinetic AFT data with traditional methods in petroleum geosciences can help unravel complex thermal histories of sedimentary basins. Applying these methods elsewhere can improve the characterisation of petroleum systems.

How to cite: Spalding, J., Powell, J., Schneider, D., and Fallas, K.: Resolving thermal histories via multi-kinetic apatite fission track data: A case study from Phanerozoic strata within the Peel Plateau NWT, Canada, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3135, https://doi.org/10.5194/egusphere-egu21-3135, 2021.

11:10–11:12
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EGU21-12030
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ECS
Liu Xiaoyan, Yuan Sihua, Jin Chunsheng, Bai Xiangdong, Jiang Jiyi, Zhao Zhenghong, and Li Ying

The Yili basin, sandwiched in the Northern and Southern Tianshan Mountain, is an ideal area to study the eroded histories at the Northern Tianshan Mountain during the late Cenozoic. Massive works have been done on tectonic deformation and uplift in this region. However, due to the lack of biostratigraphic data and effective dating marks, the uplifting time limit of the Tianshan Mountain are still argued by many researchers. In order to constrain the uplift history in the west Tianshan Mountain and provid the late Cenozoic time scale, we carried out a series of studies in the Chinese Yili Basin, fortunately, we acquired a drilling core with a depth of 500 m in the Quarternary depocenter in this basin, which provides the basis for the relevant studies. These results offered basic geological data for protecting against and mitigating earthquake disasters. 

A magnetic stratigraphic study was carried out on the drilling core, combined with three OSL dating data from a natural section adjacent to the drilling hole, an effective time scale was established. There are three main results as follows: (1)The polarity sequences shows 5 normal and 5 reverse polarity zones which can be readily correlated with the Geomagnetic Polarity Time Scale (GPTS2012), dating the core from 3.11Ma to 12Ka. (2) The B/M boundary of magnetic strata in the 500m core in western Yili basin is located in the core 80m and M/G line is located in the core 400m. (3) The sedimentation rate in the western Yili Basin increased rapidly at two periods, ~1.17 to 1.07Ma and ~2.13 to 1.77Ma. 

According to the regional reference data, the peak deposition rate in the range of ~ 2.13 to 1.77Ma is closely related to the Xiyu movement in Northwest China, as a corollary, the sedimentation rate should decrease with the end of Xiyu Movement after ~1.77Ma. Another obvious lithofacies change from ~1.17 to 1.07Ma illustrates there should be a tectonic event in the Tian shan region. This Middle Pleistocene uplift can also be evidenced by the age of volcanism in the Qaidam Basin (northeastern Tibetan Plateau), the existence of thick conglomerate deposits surrounding the uplifted plateau, and the increased sedimentation rate of lacustrine deposits in the between ~1.1 and ~0.9Ma ago, followed by the loess and marine records.

How to cite: Xiaoyan, L., Sihua, Y., Chunsheng, J., Xiangdong, B., Jiyi, J., Zhenghong, Z., and Ying, L.: Magnetostratigraphy of the Yili Basin indicates Late Cenozonic activity of the Tianshan Mountain, northwestern China, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12030, https://doi.org/10.5194/egusphere-egu21-12030, 2021.

11:12–11:14
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EGU21-2145
Haijia Lei, Xiaoming Shen, Xijun Liu, Xiudang Tang, and Shiming Zhang

The southeastern Tibetan Plateau experienced significant tectonic uplift, fault activity, climate change and reorgnization of fluvial systems during the late Cenozoic. All these processes were probably accompanied by rapid rock exhumation. Therefore, rock exhumation history in this region could provide a key to reveal the interaction between tectonics, climate and surface processes. Here, we report new apatite and zircon (U-Th)/He dates from a ~1200 m granite vertical profile, located at Shimian county in the Daliang Mountains, southeastern Tibetan Plateau. The age-elevation relationship and thermal history simulation exhibit a two-phase rock exhumation history, one at ~25 Ma (~1 km/Myr) and a second moderate exhumation from ~15 Ma to present (~ 0.2 km/Myr). This two-phase rapid exhumation history is consistent with that of Longmen Shan and Jiulong in the adjacent areas. For the first phase in Oligocene, abundant geological evidence indicates that it was related to the regional uplift caused by the transpressional deformation during India-Asia convergence. However, there are two distinct explanations for the rapid exhumation from ~15 Ma to present: one group suggested this exhumation was related to the rapid river incision caused by regional uplift; By contrast, based on paleo-altimetry data another group proposed the uplift was ceased before the late Miocene in southeastern Tibetan Plateau, and then the enhanced rainfall caused by the East Asian monsoon resulted in rapid exhumation since the Middle Miocene. Our study suggests that the fast exhumation in southeastern Tibetan Plateau since ~15 Ma cannot be attributed solely to the regional uplift or the intensification of Asian monsoon. Combined with the activity history of the Anninghe fault in the study area and the East Asian monsoon evolution history, we suggest that the regional rock exhumation of southeastern Tibetean Plateau since the Middle Miocene could be the result of the combination of tectonic activity and climate change.

How to cite: Lei, H., Shen, X., Liu, X., Tang, X., and Zhang, S.: Late Cenozoic two-phase rapid exhumation of the Daliang Mountains, Southeastern Tibetan Plateau, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2145, https://doi.org/10.5194/egusphere-egu21-2145, 2021.

11:14–11:16
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EGU21-16290
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ECS
Prerna Gahlaut and Ramesh Chandra Patel

Substantial set of recent documentation with sophisticated statistical and analog models have recognized dynamic interchange between subsurface crustal distortion and exogenic erosional processes as the root of geomorphic evolution of Himalaya. Low temperature thermochronology provides insights to enumerate nature and timing of tectonic course from extracted thermal records of vertical moving rock block over geological past. In present study, we used Apatite fission track technique to calculated exhumation rates of Yamuna valley, Garhwal Himalaya. AFT ages of Lesser Himalaya Sequence of Purola region various between 4.0 ±0.8 myr to 9.5±0.6 myr. While AFT ages of LHS along Yamuna River varies form 2.3±0.5 myr to 5.6±0.6 myr and exhumation rates are 2.3-1.2 mm/yr. calculated age of Apatite sample near Main Central Thrust (MCT) is 2.3±0.5 myr which exhumed at the rate of 2.3 mm/yr. Exhumation rates of Purola region are 0.8-1.6 mm/yr.

To link the exhumation rates with present day morphology we used 2 methods; 1) Calculate morphotectonic parameters of Yamuna River valley; 2) compare our AFT ages and exhumation rates with early studies. Drainage pattern in the tectonically active zone is vigorously susceptible to mechanisms such as folding, faulting and basin tilting. Such deformation processes influence the phase of geomorphology, drainage pattern, river incision, elongation, asymmetry, and diversion. Mathematical quantification of drainage morphology elucidate spatio-temporal effect of tectonics. Morphotectonic parameters are stream length gradient index (SL), valley floor height to width ratio (Vf), asymmetry factor (Af), basin shape index (BS) and hypsometric integral (HI) extracted from SRTM DEM with resolution of 30m and are calculated in ArcGIS 10.3. These parameters further integrated to define a single Indaex of relative Active Tectonic (IRAT). Value of IRAT is very high in upper Yamunotri region and low to moderate in Purola region. The exhumation rates are further compared with erosion rates from early studies. Erosion rates derived from 10Be nuclides (Scherler et al 2014) show very slow erosion rate in Purola region (~ 0.13±0.01 mm/yr) while for Yamunotri region higher erosion rate (>4.9 mm/yr) is recorded. These erosion rates are attributed to subsurface geometry of MCT.

All three approaches together construct an evolution record of study area over geological past.  Exhumation history of Apatite and erosion rates from early studies conclude Yamuna river valley, specifically upper region of valley is very active while Purola region is less active. Morphotectonic parameters harmoniously present similar picture. These combined study point toward relegate control of climate and dominance of ongoing sub-surficial deformation along MCT in Yamuna River valley on geological time scale.

How to cite: Gahlaut, P. and Chandra Patel, R.: Insights of Spatiotemporal evolution of Yamuna Valley, Garhwal Himalaya: Derived from Fission track dating and Morphotectonic analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16290, https://doi.org/10.5194/egusphere-egu21-16290, 2021.

11:16–11:18
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EGU21-9121
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ECS
Nicolas Perez-Consuegra, Richard Ott, Gregory D. Hoke, Jorge Pedro Galve, and Jose Vicente Pérez–Peña

The tropical Northern Andes of Colombia are one the world's most biodiverse places, offering an ideal location for unraveling the linkages between the geodynamic forces that build topography and the evolution of the biota that inhabit it. In this study, we utilize a geomorphic analysis to characterize the topography of the Western and Central Cordilleras of the Northern Andes. We supplement our topographic analysis with erosion rate estimates based on gauged suspended sediment loads and river incision rates from volcanic sequences. In the northern segment of the Central Cordillera, an elevated low-relief surface (2,500m in elevation, ~40x110 km in size) with uniform lithology and surrounded by knickpoints, indicates a recent increase in rock and surface uplift rate. Whereas, the southern segment of the Central Cordillera shows substantially higher local relief and mostly well graded river profiles consistent with longer term uplift stability. These changes in the topography fit with the proposed location of a slab tear and flat slab subduction under the northern Central Cordillera, as well as with a major transition in the channel slope of the Cauca River. We identify several areas of major drainage reorganization, including captures and divide migrations that are supported by our erosion and incision rate estimates. We identify slab flattening as the most likely cause of strong and recent uplift in the Northern Andes leading to ~2 km of surface uplift since 8–4 Ma. Large scale drainage reorganization of major rivers is probably mainly driven by changes in upper plate deformation in relation to development of the flat slab subduction geometry; however, other factors such as climate and emplacement of volcanic rocks likely play secondary roles in this process. Several isolated biologic observations above the area of slab flattening suggest that surface uplift isolated former lowland species on the high elevation plateaus, and drainage reorganization may have driven diversification of aquatic species.

How to cite: Perez-Consuegra, N., Ott, R., Hoke, G. D., Galve, J. P., and Pérez–Peña, J. V.: Topographic response to Neogene variations in slab geometry, climate and drainage reorganization in the Northern Andes of Colombia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9121, https://doi.org/10.5194/egusphere-egu21-9121, 2021.

11:18–11:20
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EGU21-3520
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ECS
Hervé Guillon, Belize Lane, Colin F. Byrne, Gregory B. Pasternack, and Samuel Sandoval Solis

Roughness is paramount in Earth sciences, and landscapes, laboratory alluvial fans, river bed elevation, bedload transport and the friction laws of fluid mechanics all exhibit a fractal behavior described by a scale-persistent roughness. Yet, for a given landscape, the exact meaning of statistical roughness, or fractal dimension, remains unclear. The fractal dimension of topography is mainly understood as two end-members: at large spatial scales, it describes tectonic processes; at small spatial scales it describes erosion processes. In this study, we nuance this description by identifying the spatial scale at which erosion processes are inadequately described by fractal dimension and provide quantitative bounds on the meaning of the statistical roughness of topography at scales from 0.25 km to 100 km using three lines of evidence. First, we leverage spatial statistics to evaluate the auto-correlation structure of topographic statistical roughness across the physiographically diverse state of California, USA. Second, we identify the down-slope and across-slope directions using two-dimensional Fourier analysis, and measure the anisotropy of topography by evaluating statistical roughness in each direction. Third, we perform a spatial correlation analysis between statistical roughness and the Péclet number which describes the balance between diffusion and incision processes. Our preliminary results indicate that correlation between statistical roughness and Péclet number fades at scales greater than 4.6 km. In addition, auto-correlation saturation occurs for statistical roughness at scales greater than 16.5 km. Hence our analysis provides a more nuanced description of the statistical roughness of topography: it represents erosion processes at scales up to 4.6 km while being dominated by tectonics at scales greater than 16.5 km.

How to cite: Guillon, H., Lane, B., Byrne, C. F., Pasternack, G. B., and Sandoval Solis, S.: Evaluating the influence of erosion and tectonic processes on California’s topography by measuring its fractal dimension and anisotropy across scales, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3520, https://doi.org/10.5194/egusphere-egu21-3520, 2021.

11:20–11:22
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EGU21-3281
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solicited
Alison Duvall, Phaedra Upton, Camille Collett, Sarah Harbert, Seth Williams, Rebecca Flowers, Gregory Tucker, John Stone, and Sean LaHusen

The landscape at the NE end of the South Island, New Zealand, records oblique plate collision over the last 25 million years. Using low-temperature thermochronology, geomorphic analyses, and cosmogenic 10Be data, we document the landscape response to tectonics over long (106) and short (102 – 103) timescales in the Marlborough Fault System (MFS) and related Kaikōura Mountains. Our results indicate two broad stages of landscape evolution that reflect a changing plate boundary through time. In the eastern MFS, Miocene folding above blind thrust faults generated prominent Kaikōura Mountain peaks and formed major transverse rivers early in the plate collision history. By the Pliocene, rotation of the plate boundary led to a transition to dextral strike-slip faulting and widespread uplift that led to cycles of river channel offset, deflection and capture of tributaries draining across active faults, and headward erosion and captures by major transverse rivers within the western MFS. Despite clear evidence of recent rearrangement of the western MFS drainage network, rivers in this region still flow parallel to older faults, rather than along orthogonal traces of younger, active strike-slip faults. Such drainage patterns emphasize the importance of river entrenchment, showing that once rivers establish themselves along a structural grain, their capture or avulsion becomes difficult, even when exposed to new weakening and tectonic strain. Over short timescales (hundreds to thousands of years), apparent catchment-wide average erosion rates derived from 10Be data show an increase from SW to NE, along strike of the Seaward Kaikōura Range. These rates mirror spatial increases in elevation, slope, channel steepness, and coseismic landslides, demonstrating that both landscape and geochronology patterns are consistent with an increase in rock uplift rate toward a subduction front that is presently locked on its southern end. Remarkably, the form of the topography, hillslopes, and rivers across much of the MFS appears to faithfully record the complex and changing tectonic history of a long-lived, oblique convergent plate boundary.

How to cite: Duvall, A., Upton, P., Collett, C., Harbert, S., Williams, S., Flowers, R., Tucker, G., Stone, J., and LaHusen, S.: Landscape Records 25 Million Years of Tectonic Evolution at an Oblique Convergent Margin, Marlborough Fault System, New Zealand, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3281, https://doi.org/10.5194/egusphere-egu21-3281, 2021.

11:22–11:24
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EGU21-6089
Liran Goren, Matanya Hamawi, Amit Mushkin, and Tsafrir Levi

Rectangular drainage networks are characterized by right-angle channel bends and confluences. The formation of the rectangular pattern is commonly associated with orthogonal sets of fractures, making rectangular drainages an outstanding example of structurally controlled landform evolution. However, the association between geologic structures and rectangular patterns remains circumstantial. So far, no specific mechanisms were suggested to explain the linkage between the emergent right-angle bends and confluences and the preexisting fracture system. This gap is particularly significant for planetary rectangular drainages, where the association with preexisting structures can not be directly observed.

We investigated the mechanistic linkages between geologic structures and the geomorphic drainage pattern in the hyper-arid Ami'az Plain located within the Dead Sea Basin in SE Israel. The Ami'az Plain is incised by a seemingly rectangular canyon system and is also penetrated by hundreds of sub-vertical clastic dikes (mode-I opening cracks infilled with sedimentary material), that reach a width of up to 0.18 m. Additionally, many caves and cavities extend from the banks and heads of the canyon system. Based on field surveys and analysis of a high resolution LiDAR based DEM, we mapped and characterized the Ami’az Plain drainage network and associated geomorphic structures including sinkholes. Our analysis revealed that the canyon system exhibits rectangular characteristics and its tributaries share dominant orientations with the strike of the clastic dikes. Surface and subsurface mapping assisted by Ground scanning LiDAR, together with field experiments, demonstrated that the caves and sinkholes are spatially associated with clastic dikes and that the caves formed by piping erosion along dikes.

Based on these findings, we propose a three-component hydrologic-geomorphic model for the formation of the Ami’az Plain rectangular drainage network: First, clastic dikes act as efficient infiltration pathways for surface runoff into the subsurface, where subsurface flow along clastic dikes induces internal erosion and forms piping caves. Second, collapses of cave roofs create sinkholes. Coalescence of sinkholes and seepage erosion in places where dikes intersect canyon banks and canyon heads generate new tributaries and extend existing ones. Finally, fluvial erosion and bank collapse modify the drainage network. Our observations and model emphasize the critical role of subsurface erosion and the formation of caves and sinkholes in linking fractures to drainage pattern evolution. This linkage could be highly consequential for our understanding of rectangular drainage evolution on planetary and terrestrial surfaces.